Many blood pressure devices, such as sphyghmomanometers, are adapted to both automatically monitor and measure a patient's blood pressure. In this type of system, a flow circuit is used to inflate and deflate a cuff that is placed over a body extremity of a patient such as a finger, an arm or a leg. The cuff typically is inflated to a predetermined pressure and is then deflated to release the pressure exerted on the extremity. Blood pressure readings are taken, either during the inflation phase of the cycle or the deflation phase, to obtain the patient's systolic and diastolic pressure.
These automatic blood pressure devices oftentimes must be employed under adverse conditions where ambient air is heavily contaminated with particulate materials, water or a combination of both which can find its way into the system through the housing enclosing the system or the air inlet and exhaust ports to the systems flow circuit. As disclosed in U.S. Pat. No. 6,450,966 B1 to Hanna, which discloses an automatic blood pressure measuring system, filters have been employed in prior art systems of this type to prevent contaminants from being carried into the system by the air supply stream entering the flow circuit. The filters used in these prior art systems are relatively small in size and are typically placed inside of the air tubing. In many cases the filters are unable to efficiently block moisture or water from getting to the working components of the system through the flow circuit. When used in a heavily contaminated area or outdoors during periods of heavy fog, rain or snow the filters quickly become clogged producing erroneous pressure readings and eventually the system fails. These prior art devices generally do not place filters at or near the exhaust port of the system and here again dust, dirt, rain, snow and other types of airborne contaminates can pass into the system through the exhaust section of the system to clog valves and contaminate sensors. Lastly, the prior art devices do not provide any means to clean the filters while the blood pressure device is in use. Once a filter becomes clogged, the procedure in progress must be terminated so that the clogged filter can be cleaned or replaced before the procedure can once again be started. Contamination induced failures of automatic blood pressure monitoring and measuring devices are most likely to occur during natural or man made disasters, a time when this kind of information is most needed. In addition, life expectancy of a blood pressure machine that has experienced a number of contaminated related failures can be expected to be foreshortened because of the additional strain that is placed on the working components of the system due to the presence of such contaminants.